CODEWITHSUNDEEP
dynamicsas
pinegulf
pinegulf

Reputation: 1396

Input value If macro variable exists else some other value

The need is to perform valuation of a macro variable outside datastep and depending on the existence of the variable, perform insertion: 

data my_dataSet; 
set ...
....
if %SYMEXIST(Variable_from_prior_code) = 1 then do;

    dataset_variable = &Variable_from_prior_code.;

    end;
else do;

    dataset_variable = &Some_default_value_from_prior_code;

end;

However, this fails at compiler when trying to run it as the " Apparent symbolic reference &Variable_from_prior_code." has not been resolved. Ie. the compiler checks the contents of the if statement even as the condition is not met.

I came up with silly work-around: to approach this from opposite directon, but feels more stupid than bag of badgers:

if %SYMEXIST(Variable_from_prior_code) = 0 then do; 

    dataset_variable = &Some_default_value_from_prior_code

    %let Variable_from_prior_code=0; /*Dummy value*/

    end;
else do;

    dataset_variable = &Variable_from_prior_code.;

end;

Any way to restrict the compiler from evaluating content, which it shouldn't due to condition? Or alternatively, more elegant work-around, which do not require creation of the variable?

Upvotes: 0

Views: 641

Answers (1)

Allan Bowe
Allan Bowe

Reputation: 12691

I'd say, avoid macro logic unless necessary! Here's a pure data step approach:

%symdel Variable_from_prior_code; /* make sure variable does not exist */
%let Some_default_value=test; /* populate macro variable */

data my_dataSet; 
  if SYMEXIST('Variable_from_prior_code') = 1 then do; /* use data step function */
    /* note variable name is quoted, else would reference a data step variable value */
    dataset_variable = symget('Variable_from_prior_code'); 
  end;
  else do;
    /* had to shorten this name to less than max allowed 32 chars */
    dataset_variable = symget('Some_default_value'); 
  end;
run;

As Tom mentions, you are currently mixing up macro and data step logic. Macro is used to write data step code (so is essentially a program generator), and that resultant data step code is executed long after the macro statements are compiled / resolved / executed.

Upvotes: 1

Related Questions